An ongoing concern with known chemical vapor deposition reactors is contamination of a workpiece in a reactor from processing gases, reaction byproducts or particulates. Sources of contaminants include processing gases and reaction byproducts from previous or adjacent reactions, and particulates deposited on reactor surfaces. A known, standard CVD reactor has a single reaction chamber. A substrate being processed in such a CVD reactor is surrounded by the physical walls of the chamber. Particulates deposited on the walls of the chamber can detach from the walls and contaminate a substrate being processed in the chamber. Some particulates arise from chemical reactions of reactant gases that are not in the desired locations on the substrate. These are internal contaminants. Other particulates are from external sources not associated with reactant gases. These are external contaminants. Multichamber CVD reactors can have cross-contamination of reactant gases, reaction byproducts and particulates from one chamber to or from another chamber, and from any of the chambers to or from the physical walls of the CVD reactor or from external sources. All contaminants are problematic. A know nitrogen purge curtain between adjacent reaction chambers alleviates some of the contamination in a multichamber CVD reactor.
U.S. Pat. No. 5,122,391 discloses an atmosphere pressure chemical vapor deposition system that has a conveyor belt and drive system for continuous processing through one or more reaction chambers separated by nitrogen purge curtains. The system has an enclosure surrounding the reaction chambers and a conveyor belt running past the chambers. Nitrogen purge curtains are placed between adjacent chambers. The process runs continuously, with the conveyor belt moving continuously at about 380 millimeters per minute. In the main reaction chamber, an injector establishes a laminar gas flow over the surface of the substrate in the atmospheric pressure chemical vapor deposition (APCVD) process.
It is a goal of the present invention to further decrease exposure to contamination in a CVD reactor, for a substrate undergoing processing in the reactor.